U.S. patent application number 17/689627 was filed with the patent office on 2022-06-16 for reliability handling for wireless transceivers.
The applicant listed for this patent is TEXAS INSTRUMENTS INCORPORATED. Invention is credited to Sarma Sundareswara GUNTURI, Eeshan MIGLANI, Narasimhan RAJAGOPAL, Jawaharlal TANGUDU, Jagannathan VENKATARAMAN.
Application Number | 20220190856 17/689627 |
Document ID | / |
Family ID | |
Filed Date | 2022-06-16 |
United States Patent
Application |
20220190856 |
Kind Code |
A1 |
GUNTURI; Sarma Sundareswara ;
et al. |
June 16, 2022 |
RELIABILITY HANDLING FOR WIRELESS TRANSCEIVERS
Abstract
Techniques maintaining receiver reliability, including
determining a present attenuation level for an attenuator, wherein
the attenuation level is set by a gain controller, determining a
relative reliability threshold based on the present attenuation
level, receiving a radio frequency (RF) signal, determining a
voltage level of the received RF signal, comparing the voltage
level of the received RF signal to the relative reliability
threshold to determine that a reliability condition exists, and
overriding, in response to the determination that the reliability
condition exists, the present attenuation level set by the gain
controller with an override attenuation level based on the present
attenuation level.
Inventors: |
GUNTURI; Sarma Sundareswara;
(Bengaluru, IN) ; VENKATARAMAN; Jagannathan;
(Bengaluru, IN) ; TANGUDU; Jawaharlal; (Bengaluru,
IN) ; RAJAGOPAL; Narasimhan; (Chennai, IN) ;
MIGLANI; Eeshan; (Chhindwara, IN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
TEXAS INSTRUMENTS INCORPORATED |
Dallas |
TX |
US |
|
|
Appl. No.: |
17/689627 |
Filed: |
March 8, 2022 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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17112137 |
Dec 4, 2020 |
11303312 |
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17689627 |
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International
Class: |
H04B 1/10 20060101
H04B001/10; H04B 1/40 20060101 H04B001/40; H03G 3/30 20060101
H03G003/30; H04B 1/12 20060101 H04B001/12 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 5, 2019 |
IN |
201941050156 |
Claims
1. A receiver comprising: an RF peak detector coupled to a
reliability detector wherein the RF peak detector is configured to:
receive a radio frequency (RF) signal; and determine a voltage
level of the received RF signal; wherein the reliability detector
module is configured to determine a relative reliability threshold
based on a present attenuation level; an override value module
coupled to the reliability detector module configured to: compare
the voltage level of the received RF signal to the relative
reliability threshold to determine that a reliability condition
exists; and override, in response to the determination that the
reliability condition exists, the present attenuation level set by
the gain controller with an override attenuation level based on the
present attenuation level; and a gain compensation value module
coupled to the override value module wherein the gain compensation
value module is configured to set the present attenuation level for
an attenuator.
2. The receiver of claim 1, wherein the override value module is
further configured to update the relative reliability threshold
based on the override attenuation level.
3. The receiver of claim 1, wherein the attenuator is coupled to a
RF analog to digital converter (RF-ADC) and wherein the receiver
includes one or more gain compensation modules configured to apply
a gain compensation to an output signal of the RF-ADC.
4. The receiver of claim 3, wherein an amount of gain compensation
is based on the override attenuation level and present attenuation
level.
5. The receiver of claim 4, wherein the override value module is
further configured to: receive an updated attenuation level from
the gain controller; and determine to release the override based on
at least one of: a maximum time duration; an indication from a peak
detector; or a comparison between the updated attenuation level,
the override attenuation level, and a decay threshold.
6. The receiver of claim 4, wherein the override value module is
further configured to: receive an updated attenuation level from
the gain controller; determine not to release the override based on
a comparison between the updated attenuation level and a decay
threshold; and update the gain compensation based on the updated
attenuation level.
7. The receiver of claim 3, wherein the receiver further comprises
a gain compensation module coupled to a peak detector wherein the
gain compensation module is configured to apply a gain compensation
to an output from the peak detector.
8. The receiver of claim 1, wherein the override value module is
further configured to: determine to apply an absolute reliability
threshold based on a comparison between an absolute reliability
threshold and the relative reliability threshold for the present
attenuation level; and wherein the reliability detector is
configured to compare the voltage level of the received RF signal
to the absolute reliability threshold to determine that an absolute
reliability condition exists; and wherein the override value module
is further configured to override, in response to the determination
that the absolute reliability condition exists, based on an
absolute reliability attenuation level.
9. An electronic device comprising: one or more processors; a
memory; an RF peak detector coupled to a reliability detector
wherein the RF peak detector is configured to: receive a radio
frequency (RF) signal; and determine a voltage level of the
received RF signal; wherein the reliability detector module is
configured to determine a relative reliability threshold based on a
present attenuation level; an override value module coupled to the
reliability detector module configured to: compare the voltage
level of the received RF signal to the relative reliability
threshold to determine that a reliability condition exists; and
override, in response to the determination that the reliability
condition exists, the present attenuation level set by the gain
controller with an override attenuation level based on the present
attenuation level; and a gain compensation value module coupled to
the override value module configured to set the present attenuation
level for an attenuator.
10. The electronic device of claim 9, wherein the override value
module is further configured to update the relative reliability
threshold based on the override attenuation level.
11. The electronic device of claim 9, wherein the attenuator is
coupled to a RF analog to digital converter (RF-ADC) and wherein
the receiver includes one or more gain compensation modules
configured to apply a gain compensation to an output signal of the
RF-ADC.
12. The electronic device of claim 11, wherein an amount of gain
compensation is based on the override attenuation level and present
attenuation level.
13. The electronic device of claim 11, wherein the override value
module is further configured to: receive an updated attenuation
level from the gain controller; and determine to release the
override based on at least one of: a maximum time duration; an
indication from a peak detector; or a comparison between the
updated attenuation level, the override attenuation level, and a
decay threshold.
14. The electronic device of claim 12, wherein the override value
module is further configured to: receive an updated attenuation
level from the gain controller; determine not to release the
override based on a comparison between the updated attenuation
level and a decay threshold; and update the gain compensation based
on the updated attenuation level.
15. The electronic device of claim 11, wherein the receiver further
comprises a gain compensation module coupled to a peak detector
wherein the gain compensation module is configured to apply a gain
compensation to an output from the peak detector.
16. The receiver of claim 9, wherein the override value module is
further configured to: determine to apply an absolute reliability
threshold based on a comparison between an absolute reliability
threshold and the relative reliability threshold for the present
attenuation level; and wherein the reliability detector is
configured to compare the voltage level of the received RF signal
to the absolute reliability threshold to determine that an absolute
reliability condition exists; and wherein the override value module
is further configured to override, in response to the determination
that the absolute reliability condition exists, based on an
absolute reliability attenuation level.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a Continuation of U.S. patent
application Ser. No. 17/112,137, filed Dec. 4, 2020, which claims
priority to India Provisional Application No. 201941050156, filed
Dec. 5, 2019, entitled, "RX/FB Relative Reliability Handling in
Wireless Transceivers", which are hereby incorporated by
reference.
BACKGROUND
[0002] Wireless systems usually include wireless transceivers used
to transmit and receive wireless signals. Often these transceivers
need to be able to support a relatively wide dynamic range of
received signal power, for example with a power level of -60 dBm to
20 dBm. To help support wide dynamic ranges, these transceivers
often include low noise amplifiers (LNAs) which provide
amplification to the received signals. Generally, gain refers to a
ratio between output voltage and input voltage. These LNAs often
include a gain setting that may be adjusted by an automatic gain
controller (AGC), which can be used to help prevent damaging
components of the transceivers, such as a digital step attenuator
(DSA), by reducing the gain when a relatively high-voltage signal
is received. For example, to receive a high voltage signal, the
gain of an LNA and/or an adjustable gain of the DSA may be adjusted
by the AGC. However, certain relatively high-voltage signals may be
a concern. When a relatively high gain setting is used to help
receive a relatively low voltage signal and a relatively
high-voltage signal, such as from a very close transmitter, is
received, the AGC may not be able to adjust the DSA gain quickly
enough and the DSA may be damaged. Additionally, high voltage
levels over some relatively long periods of time can cause
transceivers to be saturated, resulting in potential reliability
issues.
SUMMARY
[0003] This disclosure relates to a technique related to
maintaining receiver reliability, including determining a present
attenuation level for an attenuator, wherein the attenuation level
is set by a gain controller. The technique further includes
determining a relative reliability threshold based on the present
attenuation level, receiving a radio frequency (RF) signal, and
determining a voltage level of the received RF signal. The
technique further includes comparing the voltage level of the
received RF signal to the relative reliability threshold to
determine that a reliability condition exists. The technique
further includes overriding, in response to the determination that
the reliability condition exists, the present attenuation level set
by the gain controller with an override attenuation level based on
the present attenuation level.
[0004] Another aspect of the present disclosure relates to a
receiver comprising a gain controller configured to set a present
attenuation level for an attenuator. The receiver may also include
a reliability detector module configured to determine a relative
reliability threshold based on the present attenuation level. The
receiver may also include a detector configured to receive a radio
frequency (RF) signal, and determine a voltage level of the
received RF signal. The receiver may also include an override value
module configured to: compare the voltage level of the received RF
signal to the relative reliability threshold to determine that a
reliability condition exists, and override, in response to the
determination that the reliability condition exists, the present
attenuation level set by the gain controller with an override
attenuation level based on the present attenuation level.
[0005] Another aspect of the present disclosure relates to an
electronic device comprising one or more processors, a memory, and
a reliability detector module configured to determine a relative
reliability threshold based on a present attenuation level. The
electronic device may also include a detector configured to:
receive a radio frequency (RF) signal and determine a voltage level
of the received RF signal. The electronic device may also include
an override value module configured to: compare the voltage level
of the received RF signal to the relative reliability threshold to
determine that a reliability condition exists and override, in
response to the determination that the reliability condition
exists, the present attenuation level set by the gain controller
with an override attenuation level based on the present attenuation
level.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] For a detailed description of various examples, reference
will now be made to the accompanying drawings in which:
[0007] FIG. 1 illustrates an example circuit for absolute
reliability handling in wireless receivers.
[0008] FIGS. 2A and 2B illustrates an example circuits for relative
reliability handling, in accordance with aspects of the present
disclosure.
[0009] FIG. 3 is a flowchart for reliability handling, in
accordance with aspects of the present disclosure.
[0010] FIG. 4 is a flow diagram illustrating a technique for
receiver reliability handling, in accordance with aspects of the
present disclosure.
DETAILED DESCRIPTION
[0011] Wireless receivers, such as those used for wireless base
stations, evolved Node B's, access points, mobile devices, etc.,
often need to support a wide dynamic range of received, or input,
signal voltage levels. Components of the receivers, such as a DSA,
are quite sensitive and can be degraded by too high an input
voltage level. To help prevent this, and also to enhance the
supported dynamic range, receivers may include components with an
adjustable gain that may be controlled by an adjustable gain
controller (AGC). It may be understood that transceivers include
components for receiving and sending wireless signals and as the
concepts discussed herein with respect to receivers apply to
transceivers as well. The AGC may assert a signal to the LNA and/or
the DSA to reduce the gain, or even attenuate, the voltage of the
input signal based on the input voltage level to reduce the voltage
of an output of the DSA, which is then passed on to a radio
frequency analog to digital converter (RF-ADC). Attenuation
generally refers to a gain setting of less than 1, which thereby
results in a voltage level of the output signal that is smaller
than the voltage level of the input signal.
[0012] As an example, FIG. 1 illustrates an example circuit 100 for
absolute reliability handling in wireless receivers. In some cases,
absolute reliability may refer to a condition where a received
signal voltage level of an input signal is above a threshold
maximum voltage level. For example, if a device, such as a DSA, may
be damaged, and become less sensitive to input, by signal voltages
above a certain voltage level over a period of time and it is
desirable to minimize the cumulative amount of time the device is
exposed to those signal voltages above a certain voltage level. The
circuit 100 illustrates an RF sampling receiver including an LNA
114, peak detector 102, window counter 110, DSA 104, RF-ADC 106,
decimation filter chain 108 and AGC 112. The LNA 114 is coupled to
a peak detector 102 and DSA 104. The peak detector 102 is in turn
coupled to a window counter 110 and the DSA 104. The DSA is coupled
to a RF-ADC 106. The RF-ADC 106 is coupled to an AGC 112. The AGC
112 is coupled to the DSA 104 and LNA 114. It may be understood
that while FIG. 1 illustrates an RF sampling receiver, the
techniques discussed herein are also applicable to other RF
receiver designs, such as direct conversion (e.g., zero
intermediate frequency) receivers. The circuit 100 includes a peak
detector 102, but other types of detectors can be used, such as a
root mean square power detector. The peak detector 102 is
configured to detect the peak voltage level of an input signal 116.
In this example, the peak detector 102 is also configured to detect
an absolute reliability condition where a received signal voltage
level of the input signal 116 is above a threshold maximum voltage
level.
[0013] In some cases, a level of attenuation of an LNA 114 and/or
the DSA 104 may be controlled, for example, by an AGC 112 which may
be downstream of a RF-ADC 106 and a decimation filter chain 108. In
some cases, the DSA 104 may include multiple gain modes, such as a
high-gain mode or a low-gain mode, and each gain mode may provide
varying amounts of gain adjustability. For example, different gain
modes may have different ranges of gain settings and some gain
modes may have a wider range of supported gain settings than other
gain modes. The AGC 112 may be internal to the receiver circuit, or
external to the receiver circuit. Similarly, the LNA 114 may be
internal or external to the receiver circuit. Adjusting the gain of
the DSA 104 with the downstream AGC 112 may not be sufficient to
prevent reliability issues of the DSA due to an amount of time that
may be needed for the AGC to detect and respond to the absolute
reliability condition. Thus, overriding the gain setting of the AGC
may be desired. For example, where an input signal 116 is received
with a received signal voltage level above a predetermined absolute
threshold maximum level, such as voltage corresponding to 12 dBm,
the peak detector 102 may determine that an absolute reliability
condition exists and override the present attenuation level of a
DSA 104 set, for example, by the AGC. When overriding the present
DSA setting, the peak detector 102 may, for example, set the DSA
104 attenuation level to a maximum attenuation level or some other
predetermined attenuation level based on the received signal
voltage level.
[0014] In some cases, a signal with a voltage level below the
predetermined absolute threshold maximum voltage level but
sustained for a substantial period of time may also saturate the
DSA and cause relative reliability issues. As an example, a DSA, at
a certain setting may be damaged by an input signal voltage that is
lower than the voltage of the absolute reliability threshold, if
that input signal voltage is sustained over some period of time.
While a signal voltage may be below the absolute reliability
threshold, the signal voltage may be higher than a saturation level
of the DSA at some gain settings of the DSA. For example, for some
gain settings of the DSA there is a voltage level such that an
input signal beyond the voltage level will saturate the DSA. If the
input signal voltage is higher than this voltage level is sustained
for a period of time, the DSA may be damaged. To help address such
issues, a peak detector 102 may be used to detect voltage peaks
within an RF frame that may cause reliability issues. For example,
the peak detector 102 may sample input level at a particular
frequency and at each sample instance, the peak detector 102 may
output an indication (e.g., a logic high (1) if the sampled voltage
is above a threshold voltage level configured for the peak detector
102 and a logic low (0) if the sampled voltage is below the
threshold voltage level configured for the peak detector 102)
whether the sampled voltage is above a threshold voltage level. In
certain cases, the peak detector 102 voltage level threshold level
maybe configured based on, for example, the DSA attenuation
level.
[0015] Window counter 110 is incremented responsive to each
instance of a 1 from the peak detector 102. If the window counter
110 exceeds a predetermined hit threshold a reliability condition
may be asserted. In response to detection of the reliability
condition (i.e., window counter's count value exceeding the
predetermined hit threshold), the window counter 110 asserts a
signal 118 to the DSA 104 to cause the attenuation setting for the
DSA 104 to be overridden to a new attenuation setting. In some
cases, the threshold voltage level of the peak detector 102 and/or
the hit threshold of the window counter may be configurable. For
example, the hit threshold of the window counter may be a
programmable value in a register that can be set by an external
master, such as a micro-controller, serial peripheral interface,
etc. The value of the hit threshold may be determined, for example,
based on circuit design, testing, manufacturing, etc. As another
example, the hit threshold of the window counter may be a
predetermined value set as a part of circuit design, testing,
manufacturing, etc.
[0016] In some cases, after one or more RF frames are received with
a voltage level below the threshold voltage level, the window
counter 110 reliability condition may be reset. After a reliability
condition is detected, a different voltage level threshold and
window counter 110 may be set. For example, the voltage level
threshold may be reduced once the initial voltage level threshold
is hit. In some cases, the window counter 110 may count to a
release length number and accumulate a number of sample instances
received with a voltage level above the threshold voltage level.
After the release length number is reached, the accumulated number
is compared to a release threshold number. If the release condition
window counter is below the release threshold number, then the
reliability condition may be released (e.g., reset).
[0017] As transistor sizes shrink, the voltage rating of
transistors is also reduced. This reduced voltage capacity can
raise issues with relative reliability, in addition to the absolute
reliability issues discussed above. Relative reliability is related
to the voltage of a received signal as compared to a full scale
(FS) signal. For digital systems, there is a defined maximum
digital signal peak amplitude, or voltage, level, defined as 0
dBFS. This full-scale signal can vary based on a level of DSA
attenuation being applied. Generally, a signal above 0 dBFS will
saturate a receiver, but a signal above 0 dBFS but below a
predetermined absolute reliability threshold may not raise a
reliability issue. In some cases, voltage levels for a received
signal above a full-scale voltage level, but below the
predetermined absolute reliability threshold, may cause relative
reliability issues. For example, for a DSA setting of 0 dB, a
full-scale signal may be -1 dBm. If, however, an 8 dBm signal is
received, this signal is +9 dB higher than the full-scale signal or
0 dBFS voltage level supported by the DSA setting. This 8 dBm input
signal is +9 dB signal relative to the full-scale signal 0 dBFS for
the given DSA setting. This signal voltage level, while still
below, for example, a 12 dBm predetermined absolute threshold
maximum voltage level, may still cause reliability issues for the
receiver. In accordance with aspects of the present disclosure, a
reliability threshold may be determined based on a DSA attenuation
setting in addition to, or instead of, the predetermined absolute
threshold maximum voltage level.
[0018] FIG. 2A illustrates an example circuit 200 for relative
reliability handling, in accordance with aspects of the present
disclosure. Circuit 200 includes an input signal 201 input to a DSA
204 and an RF peak detector 202A. An output of the DSA 204 is
coupled to an input of RF-ADC 206. An output of the RF-ADC 206 is
coupled to an input of a decimation filter chain 208 and input of
digital peak detectors 224. An output of the decimation filter
chain 208 is coupled to an input of gain compensation module 218,
which, in turn, outputs to an AGC 212 and another circuit. An
output of the digital peak detectors 224 is coupled to an input of
a gain compensation module 220. An output of the gain compensation
module 220 is coupled to an input of the AGC 212. An output of AGC
212 is coupled to an input of an override value module 214 of a
gain controller module 222. Another output of AGC 212 is coupled to
an input of a reliability detector 210. An output of the override
value module 214 is coupled to an input of a gain compensation
value module 216 of the gain controller module 222. An output of
the gain compensation value module 216 is coupled to an input of
the gain compensation module 218 and an input of the gain
compensation module 220. An output of the override value module 214
is also coupled to an input of the DSA 204. The RF peak detector
202A is communicatively coupled to reliability detector 210 and an
output of the RF peak detector 202A may be coupled to an input of
the reliability detector 210. An output of the reliability detector
210 may pass peak detector thresholds to an input of the RF peak
detector 202A. An output of reliability detector 210 is coupled to
an input of override value module 214 and the reliability detector
210 may output a reliability indicator and a DSA setting to the
override value module 214. In certain cases, the reliability
indicator may be set to high to indicate that the DSA setting from
the reliability detector 210 should be used to override the DSA
setting from the AGC 212.
[0019] As shown, circuit 200 includes an RF peak detector 202A for
detecting the peak signal voltage level of the input signal 201, a
DSA 204, a RF ADC 206, and a decimation filter chain 208. The DSA
204 is configured to provide an adjustable amount of attenuation
for the input signal 201 based on a reliability detector 210 and an
AGC 212 in conjunction with the gain controller module 222. The
gain controller module 222 may receive gain information from the
AGC 212 as well as information from the reliability detector 210 to
determine whether the gain should be overridden. In this example,
the gain controller module 222 includes an override value module
214 for determining a gain override value and a gain compensation
value module 216 to determine a gain compensation value. In some
cases, the AGC 212 may be integrated along with other components of
circuit 200. In some cases, the AGC 212 may be coupled to, but
external to components of circuit 200, such as a part of a separate
application specific integrated circuit (ASIC). In non-override
operation, an attenuation setting of the DSA 204 is directly
controlled by the AGC 212. While the attenuation setting may be in
any form or unit, for clarity DSA settings are discussed in terms
of decibels, where decibels are 20.times.log 10(gain), where gain
is in a linear scale. Gain may be equal to the output/input voltage
in milliwatts. In this example embodiment, the AGC 212 receives a
digital signal, as converted from an analog signal to a digital
signal by the RF-ADC 206. The AGC 212 determines a DSA setting for
the DSA 204. For example, in a case where a relatively low voltage
input signal is received, the AGC 212 may determine a threshold
voltage which may saturate the DSA 204 and determine that the
relatively low voltage signal is far from saturating the DSA 204.
Based on the saturation measurement, the AGC 212 may determine an
attenuation setting for the DSA 204. For example, the AGC 212 may
utilize a lookup table, adjusting attenuation settings when the
received signal is detected above the threshold voltage and
continuing to adjust the attenuation signals if additional received
signals are still above the threshold voltage. In certain cases,
the AGC may increase the gain until the resulting voltage crosses a
first target threshold voltage and reduce the gain until the
resulting voltage crosses above a second target threshold voltage.
In this manner, the AGC may increase and/or decrease the DSA
attenuation setting (e.g., DSA gain) to maintain the signal voltage
between the first and second target thresholds, helping to maximize
a signal to noise ratio. In this example, the AGC 212 may determine
that the attenuation setting may be reduced to effectively increase
the gain applied to the input signal 201. The AGC 212 sends the DSA
setting information to the DSA 204 via the gain controller module
222 and the reliability detector 210 obtains the DSA setting
information. In some cases, the DSA setting information may include
a value from the AGC adjusting the DSA gain.
[0020] In some cases, the AGC 212 may determine the DSA setting
based on the input signal 201 signal. However, if a reliability
condition, either absolute or relative, is detected, the
reliability detector 210 may determine a different DSA setting.
FIG. 2B illustrates an example circuit for a reliability detector
210, in accordance with aspects of the present disclosure. The
reliability detector 210 may include a reliability state machine
252 for detecting and responding to reliability conditions. The
reliability state machine may be coupled to an output of the AGC
(not shown) and receive DSA setting information input from the AGC.
The reliability state machine 252 may also be coupled to and output
to a window counter controller 254. The window counter controller
254 may be communicatively coupled to a window counter 256, which
may output to an accumulator 258. The accumulator 258 may also
accept input from the RF peak detector 202A and output to a
threshold comparator 260. The threshold comparator 260 may be
communicatively coupled to the reliability state machine 252. The
reliability state machine 252 may output to the gain override
module 214.
[0021] The reliability state machine 252 may output to the window
counter controller 254, a signal indicating a window length 262
(e.g., period of time of the window). This window length 262 may
indicate a period of time to wait before resetting a window counter
if an input signal beyond the threshold voltage level is not
received within the period of time. This window length 262 may be
adjusted, for example, if an input signal beyond the threshold
voltage is received. The window counter controller 254 may receive
a counter state indication 264 from the window counter 256
indicating whether the window counter 256 is running to track a
reliability condition. The window counter controller 254 may also
assert a window reset signal 266 to the window counter 256 when the
period of time has passed. The window counter 256 may assert an
accumulator reset signal 268 to the accumulator 258 when the window
counter is being reset. The RF peak detector 202A may regularly
determine the input signal voltage level and output 270, for
example, a value, such as 1, indicating whether the input signal
voltage level is above a peak detector threshold or another value,
such as 0, indicating that the input signal voltage is below the
peak detector threshold. The accumulator 258 counts a number of
times the input signal voltage level is above the peak detector
threshold and outputs this number to the threshold comparator 260.
The reliability state machine 252 may also output to the RF peak
detector 202A and set the peak detector thresholds 272. The
threshold comparator 260 determines whether the reliability
condition is still present by monitoring the output of the
accumulator 258 for changes to the number of times the input signal
voltage level is above the peak detector threshold within a number
of hits threshold 274 received from the reliability state machine
252. The threshold comparator 260 may output 276 to the reliability
state machine 252 indicating whether the reliability condition is
present. Based on output 276, the reliability state machine 252 may
determine if the reliability condition is present or not.
[0022] Returning to FIG. 2A, based on the DSA setting information,
the reliability detector 210 determines a relative reliability
threshold. In some cases, the relative reliability thresholds may
differ for some or each of the DSA settings. As an example, the
relative reliability threshold may be configured to be 9 dB higher
than the voltage level of 0 dBFS of the present DSA gain. Thus, as
a more specific example, where the present DSA setting is 0 dB the
0 dBFS voltage level, which, in this example, corresponds to -1
dBm, the relative reliability threshold, if configured to be 9 dB
higher than the voltage level of 0 dBFS, at the present DSA setting
of 0 dB would correspond to 8 dBm. In some cases, the relative
reliability thresholds for the DSA settings may be configurable or
programmable, or based on a particular hardware configuration, such
as the external AGC type, RF-ADC type, DSA type, or bands being
received. For example, a set of registers or a lookup table may be
provided to store the relative reliability thresholds and these
registers may be externally accessible to allow the relatively
reliability thresholds to be adjusted. The relative reliability
thresholds may be, in some cases, predetermined and stored in a
memory.
[0023] Once a relative reliability threshold is determined for a
present DSA setting, a voltage level for a received signal, as
determined by the peak detector 202A, is compared to the relative
reliability threshold. In some cases, the peak detector 202A may be
configured to regularly determine the input signal voltage level,
such as 128 or 256 times per second, and output this signal voltage
level information to the reliability detector 210. For example, the
peak detector can regularly output a binary signal with a value
indicating whether the input signal voltage level is above or below
the relative reliability threshold. The reliability detector 210
may receive the signal voltage level information and count a number
of instances in which the signal voltage level exceeds the relative
reliability threshold for a given time period. If the number of
instances exceeds a number of peaks (e.g., number of instances
where the signal voltage level exceeds the relatively reliability
threshold) threshold, the reliability detector 210 may determine
that the received signal has exceeded the relative reliability
threshold and that a relative reliability condition exists. In some
cases, the number of peaks threshold may be configurable, for
example by a user. For example, one or more registers may be
provided to store the number of peaks threshold and these registers
may be externally accessible to allow the a number of peaks
thresholds to be adjusted.
[0024] Returning to the earlier example where the relatively low
voltage signal is being received, another transmitter may start to
transmit a relatively high-voltage signal to the receiver. This
relatively high-voltage signal may be received and the voltage
level for the received signal may be determined to exceed the
relative reliability threshold based on, for example, twenty
instances over a course of 128 measurements of the peak detector to
be 9 dB, higher than the 0 dBFS voltage level, at the present DSA
setting of 0 dB, of -1 dBm.
[0025] If the voltage of a received signal exceeds the relative
reliability threshold, an override value module 214 may determine a
gain override value. In some cases, this gain override value may be
based on the present DSA setting and/or as an offset value from the
present DSA setting. In some cases, the gain override value may be
based on the relative reliability threshold. For example, the gain
override value may be determined based on a difference between the
relative reliability threshold for the present DSA setting and the
voltage level for the received signal. Returning to the previous
example, as the received signal has a voltage level of 9 dBm and
the relative reliability threshold is 8 dBm, the gain override
value may be determined to be 1 dB. In other cases, the gain
override value may be configurable. As a second example, if an
incoming signal voltage level is 9 dBm and the relative reliability
threshold is 8 dBm for a 0 dB DSA setting, the override gain value
may be determined to be 9 dB. Once the gain override value is
determined, the present DSA setting is overridden based on the gain
override value. Returning to the previous example, the present DSA
setting of 0 dB may then be overridden and set to an overridden DSA
setting of 1 dB. In the second example, the present DSA setting of
0 dB may be overridden and set to the overridden DSA setting of 9
dB.
[0026] Overriding the AGC 212 settings for the DSA 204 could, in
some cases, result in undesirable feedback loops. For example, if
the present DSA setting is overridden to increase the DSA settings,
attenuation is increased, which effectively reduces the gain of
received input signals and saturation of the DSA 204. If the AGC
212 detects that saturation has decreased, the AGC 212 may attempt
to lower the DSA setting, thereby increasing the amplitude of the
signal provided to the RF-DAC 206. Gain compensation may be used to
help address such potential feedback loops. A gain compensation
value module 216 determines a gain compensation value. In some
cases, the gain compensation value may be based on the gain
override value determined by the override value module 214. The
gain compensation value module 216 may, in some cases, be combined
with the override value module 214. In some cases, the AGC 212 may
be coupled downstream of the decimation filter chain 208. In such
cases, a gain compensation module 218, coupled between the
decimation filter chain 208 and the AGC 212, may apply gain
compensation to a digital signal input to the gain compensation
module 218, effectively increasing a gain of an output digital
signal 226. In some cases, the AGC 212 may be coupled 228 upstream
of the decimation filter chain 208 to directly sample a digital
version of the received analog signal. In some cases, the gain
compensation module 220 may be configured to support a higher
bandwidth, such as 2-3 GHz, as compared to gain compensation module
218 as the gain compensation module 220 is sampling data prior to
the decimation filter chain 208.
[0027] In some cases, the AGC 212 may receive the gain compensated
output of the gain compensation modules 218, 220 and use the output
to help the AGC 212 to effectively see that the RF-ADC 206 is
saturating. The AGC 212 may then help adjust the DSA setting
appropriately, such as by increasing the DSA attenuation setting.
In some cases, the AGC 212 may be an external AGC. As an example of
an external AGC, the AGC may be integrated as a part of a separate
circuit or chip from the RF-ADC 206, DSA 204, and decimation filter
chain 208. The external AGC, in such cases, is communicatively
coupled to the gain controller module 222.
[0028] FIG. 3 is a flow chart 300 for reliability handling, in
accordance with aspects of the present disclosure. In this example
embodiment, the flow chart 300 illustrates a technique for
detecting absolute and relative reliability conditions. In some
cases, the reliability state machine 252 of FIG. 2B may implement
the techniques shown in flow chart 300. Where a receiver is
configured to detect both absolute and relative reliability
conditions, the reliability condition being checked may be
determined, in some cases, by the DSA setting. For a particular DSA
setting, at block 302, a relative reliability threshold is
determined, for example by reliability detector 210 as discussed
above. In some cases, this threshold may be used to determine
settings for the analog RF peak detector. At decision block 304, a
determination is made, for example by reliability detector 210, as
to which threshold voltage level to use. Which threshold voltage
level to use can be expressed as a function min(voltage level at 0
dBFS (or present DSA setting)+relative reliability threshold,
absolute reliability threshold). Thus, the function finds the
minimum of either a voltage level at 0 dBFS plus the relative
reliability threshold or the absolute reliability. This expression
may be evaluated by the peak detector 202A, or the state machine
252 of FIG. 2B, to detect a relative reliability condition below a
particular DSA attenuation setting. Above the particular DSA
attenuation setting, detecting an absolute reliability condition is
given a higher preference. As an example, assume for a particular
receiver if the 0 dBFS voltage level with 0 dB DSA setting is 0 dBm
and an absolute reliability attenuation level setting at 20 dBm.
For the 12 dB DSA, the 0 dBFS voltage level would be 0+12=12 dBm.
If the relative reliability threshold is 9 dB, the relative
reliability voltage level would be 12+9=21 dBm. However, if, as in
this example, there is an absolute reliability voltage threshold at
20 dBm, the 12 dB DSA gain setting would exceed the absolute
reliability voltage threshold. In some cases, the determination of
block 304 may be included in state 302. Thus, a determination may
be made that at a DSA attenuation setting of 11 dB or higher, the
input voltage level may be checked for the absolute reliability
condition, for example, by a peak detector, at block 306 and below
the DSA attenuation setting of 11 dBm, the input voltage level may
be checked for the relative reliability condition at state 320, for
example, by another peak detector.
[0029] As a more specific example where the input voltage level is
checked for relative reliability, assume that the particular
receiver embodiment discussed in the previous example with a DSA
attenuation setting of 0 dBFS receives an input signal with a
voltage level of 10 dBm. As this input signal voltage is above the
relative reliability threshold of 9 dBm, the relative reliability
condition is detected at decision block 320 in a manner as
discussed above with respect to the reliability detector 210. In
this example, at block 322, the DSA setting is overridden based on
the determined gain override value offset corresponding to a DSA
setting of 9 dB. In some cases, an override state indicator, such
as a flag, register entry, or bit, is set indicating that the DSA
setting has been overridden. At block 324, a corresponding gain
compensation value may be determined based on the DSA override
setting, for example as an offset value. As there was a change in
the DSA settings, control returns, via decision block 334, to block
302. As the 9 dB DSA setting is still below 11 dB, input voltage
continues to be checked for relative reliability condition at
decision block 320 with a second relative reliability threshold. As
the DSA settings were changed in a first round of overriding the
DSA setting, the relative reliability threshold (e.g., the second
relative reliability threshold) is determined again at block 302.
Assuming the second relative reliability threshold is also 9 dB
above 0 dBFS at a 9 dB DSA attenuation setting, the second relative
reliability threshold is determined to be 18 dBm. Assuming the
received signal voltage continues to be measured at 10 dBm, the
received voltage is less than the 18 dBm second relative
reliability threshold, and a second relative reliability condition
is not present.
[0030] In another relative reliability example, assume an input
signal voltage measured at 21 dBm is received with the particular
receiver embodiment discussed in the previous example again with a
DSA attenuation setting at 0 dB. Similar to the first round of
overriding the DSA setting described above, as the 21 dBm input
signal voltage is above the relative reliability threshold, the
relative reliability condition is detected at decision block 320.
At block 322, the DSA is overridden based on the determined gain
override value corresponding to a DSA setting of 9 dB and an
override state indicator may be set. A corresponding gain
compensation value may be determined based on the DSA override
setting at block 324. As the 9 dB DSA setting is still below 11 dB,
input voltage continues to be checked for relative reliability
condition at decision block 320 with a second relative reliability
threshold set to 18 dBm, as discussed above.
[0031] Assuming the input signal voltage continues to be measured
at 21 dBm, a second relative reliability condition is detected at
decision block 320 and the DSA setting is again overridden by an
offset of 9 dB, the DSA setting is then set to 18 dB. As there was
a change in the DSA settings, control returns, via decision block
334, to block 302. A third relative reliability threshold is
calculated at 18 dBm+9 dB=27 dBm. At decision block 304, a new peak
detector threshold is determined where min(18 dBm+9 dB, 20 dBm)-18
dBm=2 dB higher than the 0 dBFS voltage level at 18 dB DSA
attenuation. As the DSA setting is 18 dB, which is higher than the
11 dB DSA setting, the input signal is checked for absolute
reliability and a determination whether an absolute reliability
condition exists is made at block 306 by comparing the input signal
voltage level to the absolute reliability attenuation level
threshold. Where the input signal voltage continues to be 21 dBm,
an absolute reliability condition exists and at block 308, a
determination is made to override the DSA setting. At state 310,
the DSA setting is overridden, for example, by a maximum level
setting of the DSA, or another DSA level setting based on
predetermined level. In some cases, a gain compensation value may
be applied, or the output of the decimation filter chain may be
saturated. After the reliability condition is no longer
appropriate, it may be desirable to release the DSA override.
[0032] Flowchart 300 also illustrates example techniques for
releasing the DSA override. In this example, a determination to
release the DSA override applied in response to an absolute
reliability condition may be made at decision block 312. As an
example, the determination that the DSA override should be released
may be based on a determination that the input voltage level has
dropped below the absolute reliability attenuation level threshold
or after a some period of time has passed. In some cases, this
period of time may correspond to a window length for resetting a
window counter. This period of time may be indicated to the window
counter. If the input voltage level has dropped, then the DSA
override may be removed at block 314. If gain compensation was
previously applied, or if the output of the decimation filter chain
was saturated, these may also be removed at block 314.
[0033] For a relative reliability condition, there may be multiple
techniques for releasing the DSA override. A first technique may be
based on observations of the response of the AGC. Returning to the
example discussed above with the input signal voltage measured at
10 dBm, after the DSA setting is overridden corresponding to a DSA
setting of 9 dB, at block 324, a corresponding gain compensation
value is determined at state 326. This gain compensation value may
be used to increase the gain of a digital signal received by the
AGC. In some cases, the AGC may detect an increase in the
saturation of the digital signal received and increase the
attenuation setting of the DSA. Returning to the example, after the
gain compensation value is determined, control returns, via blocks
334, 302, and 304, to decision block 320 where input signal voltage
is checked for a second relative reliability condition at decision
block 320. As the second relative reliability threshold is
determined to be 18 dBm, the input signal voltage is not sufficient
to trigger a second relative reliability condition. At decision
block 326, the override state indicator, set at block 322, may be
checked. As the override state indicator is set, a difference
between the DSA override setting and an updated DSA setting
requested by the AGC is determined at block 328. An updated gain
compensation value may also be determined based on the updated DSA
setting and the DSA override setting. At decision block 330, the
difference between the DSA override setting and an updated DSA
setting requested by the AGC is checked to see if it is less than a
decay threshold. In some cases, this decay threshold may be
configurable and may include a check to ensure that the AGC has
updated the DSA setting to increase attenuation. That the AGC has
updated the DSA setting to increase attenuation and that the
difference between the updated DSA setting and the DSA override
setting is below the decay threshold indicates that the AGC has
noticed and responded to address the relative reliability
condition. At block 332, the DSA override may be removed (e.g.,
released), along with any digital gain compensation applied, and
the override state indicator cleared. If the AGC has not updated
the DSA and/or if the difference is above the decay threshold, then
the DSA override is maintained at block 336. If necessary, the
updated gain compensation value may be used to adjust the digital
gain compensation.
[0034] Another technique for releasing the DSA override for a
relative reliability condition may be time based. For example, a
transient high-voltage input signal may trigger a relative
reliability condition resulting in a DSA override. This signal may
be just long enough to trigger the DSA override but not long enough
to be detected by the AGC. Thus, there may be a configurable
maximum time duration for the relative reliability condition, after
which the DSA override may be removed. This maximum time duration
may be configured to be relatively long and sufficient for the AGC
to have multiple opportunities to detect and react. A check to
ensure that a DSA override time duration is less than the maximum
time duration (e.g., decay threshold) may be performed at block
330, for example by a reliability detector. If the DSA override
time duration is greater than the maximum time duration, then the
DSA override is released and the DSA override time duration is
reset. If another high-voltage input signal is received, another
DSA override may be imposed.
[0035] In some cases, a receiver may include more than a single
peak detector. For example, circuit 200 in FIG. 2A may include
multiple RF peak detectors 202A and 202B. Where multiple peak
detectors are available, one of the peak detectors may be
configured to detect an absolute reliability condition and another
peak detector may be used to detect a relative reliability
condition. In such cases, the determination whether a reliability
condition and/or absolute reliability condition exists may be
performed in a manner similar to that described above. Releasing
the DSA override with multiple peak detectors may be similar to
that described above for embodiments with a single peak detector.
In some cases, with multiple peak detectors, a first peak detector
may be configured to detect both absolute and relative reliability
conditions and a second peak detector may be configured to detect
an input voltage level based on the threshold for the peak
detector. In such cases, when an override condition is present, the
second peak detector may be used to determine whether the input
voltage level has fallen below the threshold and thus the override
condition is no longer present and release the DSA override.
[0036] FIG. 4 is a flow diagram 400 illustrating a technique for
receiver reliability handling, in accordance with aspects of the
present disclosure. At block 402, a present attenuation level for
an attenuator is determined. The attenuator level indicates an
amount of attenuation to be applied to a received RF signal and may
be determined by the AGC in conjunction with a gain controller,
such as gain controller module 222, and a reliability detector,
such as reliability detector 210. At block 404, a reliability
threshold is determined based on the present attenuation level. For
example, a relative reliability threshold may be determined, for
example by a reliability detector, such as reliability detector
210, based on the present attenuation level set by the gain
controller. In some cases, this relative reliability threshold may
be based on an offset from the attenuation level and a full-scale
signal. At block 406, a radio frequency (RF) signal is received.
For example, one or more peak detectors, such as peak detector 202A
and/or peak detector 2026, may receive an analog signal from one or
more antennas. In some cases, the signal received by the peak
detectors may have been modified, such as amplified, by one or more
LNAs. In some cases, root mean square (RMS) power voltage may also
be used.
[0037] At block 408 a voltage level of the received RF signal is
determined. For example, one or more of the peak detectors may
measure a signal voltage level of the received RF signal. At block
410 the voltage level of the received RF signal is compared to the
reliability threshold to determine that a reliability condition
exists. For example, if the voltage level is equal or above a
reliability threshold power level, then a relative reliability
condition exists. In some cases, this comparison may be performed
by a reliability detector, such a reliability detector 210. At
block 410, in response to the determination that the reliability
condition exists, overriding the present attenuation level set by
the gain controller with an override attenuation level based on the
present attenuation level. For example, the DSA attenuation setting
may be overridden, by a gain controller such as gain controller
222, with a predetermined value, where the predetermined value is
based on present DSA setting.
[0038] The term "couple" is used throughout the specification. The
term may cover connections, communications, or signal paths that
enable a functional relationship consistent with the description of
the present disclosure. For example, if device A generates a signal
to control device B to perform an action, in a first example device
A is coupled to device B, or in a second example device A is
coupled to device B through intervening component C if intervening
component C does not substantially alter the functional
relationship between device A and device B such that device B is
controlled by device A via the control signal generated by device
A.
[0039] Modifications are possible in the described embodiments, and
other embodiments are possible, within the scope of the claims.
* * * * *